Preparation method and application of double-modified polyvinyl alcohol aerogel

Abstract

The invention discloses a preparation method and application of a double-modified polyvinyl alcohol aerogel. The double-modified polyvinyl alcohol aerogel is prepared by polymerizing, blending and freeze-drying fly ash stone modified with ester compounds, hydrochloric acid-modified activated carbon and polyvinyl alcohol aerogel. Span85, Span80, Span65 and Span60 are selected to modify nano-calcium carbonate contained in the fly ash stone to improve the oil absorption value of the nano-calcium carbonate. The modified fly ash stone and hydrochloric acid-modified activated carbon with a concentration of 3 to 7 mol / L are combined with the polyvinyl alcohol aerogel, and freeze-drying technology is used to obtain the double-modified polyvinyl alcohol aerogel. The double-modified polyvinyl alcohol aerogel can not only significantly improve the oil absorption rate of the material, but also can be efficiently recycled and has a high oil retention rate. Therefore, the double-modified polyvinyl alcohol aerogel has broad application prospects in the field of petroleum pollution control.

Description

Technical Field

[0001] This invention belongs to the field of petroleum pollution control, and specifically relates to a preparation method and application of a double-modified polyvinyl alcohol aerogel. Background Art

[0002] The preparation of oil-absorbing materials has been extensively studied for oil pollution control. However, traditional oil-absorbing materials, such as natural fibers, oil-absorbing resins, and diatomaceous earth, suffer from low oil absorption rates, slow oil absorption rates, low oil retention rates, and limited recyclability, limiting their application in oil pollution control.

[0003] Given the challenges of traditional oil-absorbing materials, researchers have investigated novel porous oil-absorbing materials, such as filter membranes, modified sponges, and aerogels. These materials offer advantages such as high oil absorption capacity, excellent oil-water separation, and good corrosion resistance. However, they still suffer from limitations in their oil absorption types, poor recycling rates, high production costs, and complex preparation processes, which in turn limit their application.

[0004] The Chinese patent "A method for preparing a polyacrylonitrile / reduced graphene oxide composite oil-absorbing material" cuts polyacrylonitrile fibers into 3-5mm pieces, mixes them with a reduced graphene oxide aqueous solution, and freezes them at -40±15°C for 6-12 hours to obtain a polyacrylonitrile / reduced graphene oxide composite oil-absorbing material. The composite oil-absorbing material has an oil absorption rate of up to 64.5g·g -1 Although the oil absorption rate has been improved, its recycling times are poor (it can be recycled 20 times, and the oil absorption rate is 60.2g·g -1 ) and low oil retention rate (the adsorption mass of the sample is 64.5 times its own weight).

[0005] The Chinese patent, "Process for Preparing a Rubber-Based Three-Dimensional Porous Oil-Absorbent Material," utilizes a template filtration method to prepare a three-dimensional, porous, oil-absorbent material from silicone rubber (PDMS). This porous oil-absorbent material boasts a porosity exceeding 70% and an oil absorption rate of 250% to 1750%. However, it also suffers from issues such as limited recycling rates and low oil retention, limiting its application in oil pollution control.

[0006] The Chinese patent, "A Method for Preparing a Porous Oil-Absorbent Material," uses organosiloxane as a prepolymer, along with a crosslinker, functional adjuvant, and additives, to create a porous oil-absorbent material. This porous oil-absorbent material achieves a saturated adsorption capacity of 500% to 2300% for organic solvents such as petroleum ether, but suffers from a low recyclability (up to 20 times) and poor oil retention.

[0007] The Chinese patent, "A Fully Aromatic Ring Porous Oil-Absorbent Material and Its Preparation Method," involves dissolving ferric chloride in 1,2-dichloroethane and then adding benzene, biphenyl, dimethoxymethane, and polyurethane to react to produce the porous oil-absorbing material. While this material has a strong absorption capacity for aromatic hydrocarbons, it suffers from a narrow absorption range, limiting its application in oil pollution control.

[0008] In view of the problems of the above-mentioned new porous oil-absorbing materials, it is of great research significance to design a composite aerogel oil-absorbing material that can efficiently absorb oil in a circular manner. Currently, commonly used aerogel materials include silica aerogel and polyvinyl alcohol aerogel. Among them, polyvinyl alcohol aerogel has a high specific surface area (300-1000m 2 / g), high porosity (up to 90% or more), low density (1.26-1.29 g·cm 3 ), so the present invention uses polyvinyl alcohol aerogel as the matrix, adds ester compound modified fly ash stone and hydrochloric acid modified activated carbon to construct a composite aerogel to prepare the oil absorbing material. Summary of the Invention

[0009] To solve the above technical problems, the present invention provides a preparation method and use of double-modified polyvinyl alcohol aerogel, which solves the shortcomings of existing oil-absorbing materials such as low oil absorption rate, low oil absorption cycle times, limited oil absorption types and low oil retention rate.

[0010] The technical solution of the present invention is:

[0011] A method for preparing a double-modified polyvinyl alcohol aerogel comprises the following steps:

[0012] Step 1, pretreatment of fly ash stone: using fly ash stone as raw material, selecting hydrochloric acid as pretreatment solution, the pH value of the pretreatment solution is 3.5-6.5, using double decomposition method to first mix the fly ash stone sample with the pretreatment solution and filter, adding oleic acid and ethanol solution to the filtrate and adding saturated sodium carbonate solution dropwise to obtain nano calcium carbonate precipitate, filtering, and drying to obtain nano calcium carbonate powder;

[0013] Step 2: mixing the nano-calcium carbonate powder obtained in step 1 with anhydrous ethanol, heating the mixture in a water bath, and uniformly dispersing the mixture by ultrasonication. Subsequently, one of the ester compounds Span 85, Span 80, Span 65, and Span 60 is added, followed by heating and stirring. After the reaction is completed, the mixture is cooled to room temperature and filtered, washed with anhydrous ethanol, and dried to obtain modified nano-calcium carbonate.

[0014] Step 3: First, polyvinyl alcohol powder is added to deionized water and dissolved at 80°C to 100°C to obtain a polyvinyl alcohol solution. Then, activated carbon is added to 10 to 50 mL of hydrochloric acid, stirred in a water bath at 40 to 60°C for 4 to 7 hours, washed with deionized water until neutral, filtered, and dried in a drying oven at 90°C to 120°C for 12 to 24 hours to obtain modified activated carbon. Finally, the dried modified activated carbon is dissolved and polymerized with the polyvinyl alcohol solution. During the solution polymerization process, NaOH is added dropwise to adjust the pH value to 5 to 8 to obtain a hydrochloric acid-modified activated carbon / polyvinyl alcohol hydrogel with extremely strong hydrophobicity.

[0015] Step 4, freeze-drying method to prepare ester compound modified fly ash stone / hydrochloric acid modified activated carbon / polyvinyl alcohol aerogel: the modified nano calcium carbonate obtained in step 2 is ultrasonically treated for 10 to 30 minutes, uniformly dispersed in a hydrochloric acid solution, initiator AIBN and adhesive triethanolamine are added, and mixed with the hydrochloric acid modified activated carbon / polyvinyl alcohol hydrogel obtained in step 3 to obtain ester compound-nano calcium carbonate / hydrochloric acid modified activated carbon / polyvinyl alcohol hydrogel, and the ester compound-nano calcium carbonate / hydrochloric acid modified activated carbon / polyvinyl alcohol hydrogel is dried at a temperature of -10°C to -80°C and a vacuum of 5 to 30 Pa for 12 to 24 hours to remove excess moisture and air to obtain a dry ester compound-nano calcium carbonate / hydrochloric acid modified activated carbon / polyvinyl alcohol aerogel, that is, a double-modified polyvinyl alcohol aerogel.

[0016] Furthermore, the particle size of the nano calcium carbonate powder obtained in step 1 ranges from 30 to 100 nm.

[0017] Furthermore, the drying temperature in step 1 is 40-60° C., and the drying time is 1.5-2.5 hours.

[0018] Furthermore, the mass fraction of the ester compounds Span 85, Span 80, Span 65, and Span 60 selected in step 2 is 3% or 5%.

[0019] Furthermore, the mass ratio of the nano-calcium carbonate powder to anhydrous ethanol in step 2 is 1:2 to 1:8, the water bath heating temperature is 50°C to 70°C, the ultrasonic dispersion time is 10 to 30 minutes, the heating and stirring time is 40 to 90 minutes, and the drying temperature is 90 to 120°C.

[0020] Furthermore, the hydrochloric acid concentration in step 3 is in the range of 3% to 7%, and the activated carbon mass is 2 to 8 g.

[0021] Furthermore, after the modified activated carbon in step 3 is dissolved, it is polymerized with a polyvinyl alcohol solution in a mass fraction range of 5%, 10%, 15%, and 20% for 3 to 6 hours.

[0022] Furthermore, in step 4, the mass of the initiator AIBN is 0.1-1 g, and the mass of the adhesive triethanolamine is 0.5-1.5 g.

[0023] A method for preparing double-modified polyvinyl alcohol aerogel and application of the prepared double-modified polyvinyl alcohol aerogel in petroleum pollution control.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] First, the main component of fly ash stone is calcium carbonate, which contains nano-scale calcium carbonate with a particle size between 25 and 100 nm, which has excellent oil absorption, with an oil absorption value of 122.6g / 100g. The present invention uses an ester compound to modify the nano-calcium carbonate. The ester groups in the lipophilic ester compound form a chelating effect with the free calcium ions in the nano-calcium carbonate in the fly ash stone, coating the surface of the nano-calcium carbonate to enhance its lipophilicity.

[0026] Secondly, the present invention uses hydrochloric acid with a concentration of 3 to 7 mol / L to modify activated carbon. The surface of the activated carbon is roughened by the etching effect of hydrochloric acid on the activated carbon, thereby increasing the number of porous structures and the specific surface area of the activated carbon. Through the hydrogen bonding effect between the hydrochloric acid modified activated carbon and polyvinyl alcohol, the mixed liquid is polymerized with the above-mentioned ester compound modified fly ash stone under the action of initiator AIBN and adhesive triethanolamine, and then freeze-dried to form a high porosity (porosity of more than 99%) and high specific surface area (specific surface area of 500 to 1000m 2 ·g -1 ) composite aerogel, thereby increasing the oil absorption rate of polyvinyl alcohol aerogel (the oil absorption value is 260-370g·g -1 ).

[0027] Third, the ester compound modified fly ash stone / hydrochloric acid modified activated carbon / polyvinyl alcohol aerogel of the present invention was tested for its recyclability using a cycle test experiment, and its cycle number was as high as 5000 to 5500 times, which is higher than the cycle number of existing organosilane-hydrophobic sponge.

[0028] Fourthly, the oil retention rate of the ester-modified fly ash stone / hydrochloric acid-modified activated carbon / polyvinyl alcohol aerogel of the present invention is higher than that of existing oil-absorbing materials (oil retention rate exceeding 90%). During the oil absorption process, the aerogel expands and transforms into an oleogel, further improving its oil retention rate (oil retention rate exceeding 98%). This oil-absorbing material has broad application prospects in the field of petroleum pollution control. DETAILED DESCRIPTION

[0029] The project of the present invention is described in detail below with reference to specific methods.

[0030] A method for preparing a double-modified polyvinyl alcohol aerogel is specifically implemented according to the following steps:

[0031] Step 1, pretreatment of fly ash stone: Using fly ash stone as raw material, hydrochloric acid is selected as the pretreatment solution, and the pH value of the pretreatment solution is 3.5-6.5. The fly ash stone sample and the pretreatment solution are first mixed and filtered by double decomposition method. Then, oleic acid and ethanol solution are added to the filtrate, and saturated sodium carbonate solution is added dropwise to obtain 30-100 nm nano-calcium carbonate precipitate. The precipitate is filtered and dried at a temperature of 40-60°C for 1.5-2.5 hours to obtain a dry 30-100 nm nano-calcium carbonate powder.

[0032] Step 2: mixing nano-calcium carbonate powder and anhydrous ethanol in a mass ratio of 1:2 to 1:8, heating the mixture in a water bath, heating to 50° C. to 70° C., and ultrasonicating the mixture for 10 to 30 minutes to uniformly disperse the mixture. Subsequently, one of the ester compounds Span 85, Span 80, Span 65, and Span 60 is added, heating and stirring the mixture for 40 to 90 minutes. After the reaction is completed, the mixture is cooled to room temperature and filtered, washed with anhydrous ethanol, and dried at 90 to 120° C. to obtain modified nano-calcium carbonate.

[0033] Step 3, first, adding polyvinyl alcohol powder to deionized water and dissolving it at 80°C to 100°C to obtain a polyvinyl alcohol solution, then adding 2 to 8 g of activated carbon to 10 to 50 mL of hydrochloric acid with a concentration of 3 to 7 mol / L, stirring in a water bath at 40 to 60°C for 4 to 7 hours, washing with deionized water until neutral, filtering, and drying in a drying oven at 90°C to 120°C for 12 to 24 hours to obtain modified activated carbon, and finally dissolving the dried modified activated carbon and polymerizing it with a polyvinyl alcohol solution in a mass fraction range of 5%, 10%, 15%, and 20% for 3 to 6 hours. During the solution polymerization process, NaOH is added dropwise to adjust the pH value to 5 to 8 to obtain a hydrochloric acid-modified activated carbon / polyvinyl alcohol hydrogel with extremely strong hydrophobicity;

[0034] Step 4: ultrasonically treat the dried ester compound-modified nano-calcium carbonate for 10 to 30 minutes, uniformly disperse it in a hydrochloric acid solution, add 0.1 to 1 g of initiator AIBN and 0.5 to 1.5 g of adhesive triethanolamine, and mix them with the hydrochloric acid-activated carbon / polyvinyl alcohol sol to obtain an ester compound-nano-calcium carbonate / hydrochloric acid-modified activated carbon / polyvinyl alcohol hydrogel. The composite hydrogel is freeze-dried at a temperature of -10°C to -80°C and a vacuum of 5 to 30 Pa for 12 to 24 hours to remove excess water and air, thereby obtaining a dry ester compound-nano-calcium carbonate / hydrochloric acid-modified activated carbon / polyvinyl alcohol aerogel, i.e., a double-modified polyvinyl alcohol aerogel.

[0035] Example 1

[0036] A method for preparing a double-modified polyvinyl alcohol aerogel, the specific process is as follows:

[0037] Step 1, pretreatment of fly ash stone: fly ash stone is used as raw material, hydrochloric acid is selected as the pretreatment solution, the pH value of the pretreatment solution is 3.5, and the fly ash stone sample is first mixed with the pretreatment solution by double decomposition method and filtered. Then, oleic acid and ethanol solution are added to the filtrate and saturated sodium carbonate solution is added dropwise to obtain 30nm nano-calcium carbonate precipitate, filtered, and dried at a temperature of 40°C for 2.5h to obtain dry 30nm nano-calcium carbonate powder.

[0038] Step 2: Mixing the dried nano-calcium carbonate powder with 3% by mass of an ester compound Span 85: The nano-calcium carbonate powder and anhydrous ethanol are mixed in a mass ratio of 1:2 and heated in a water bath. After heating to 50° C., ultrasonication is performed for 10 minutes to uniformly disperse the mixture. Subsequently, 3% Span 85 is added and heated and stirred for 40 minutes. After the reaction is completed, the mixture is cooled to room temperature and filtered, washed with anhydrous ethanol, and dried at 90° C. to obtain 3% Span 85-modified nano-calcium carbonate.

[0039] Step 3, 3 mol / L hydrochloric acid modified activated carbon / polyvinyl alcohol hydrogel experiment: first, add polyvinyl alcohol powder to deionized water and dissolve it at 80°C to obtain a polyvinyl alcohol solution. Secondly, add 2 g of activated carbon to 10 mL of 3 mol / L hydrochloric acid, stir in a 40°C water bath for 7 hours, wash with deionized water until neutral, filter, and dry in a 90°C drying oven for 24 hours to obtain modified activated carbon. Finally, dissolve the dried modified activated carbon and polymerize it with the polyvinyl alcohol solution at a mass fraction of 5% for 6 hours. During the solution polymerization process, NaOH was added dropwise to adjust the pH value to 4 to obtain 3 mol / L hydrochloric acid modified activated carbon / polyvinyl alcohol hydrogel.

[0040] Step 4, Preparation of 3% Span 85-nano-calcium carbonate / 3 mol / L hydrochloric acid-modified activated carbon / polyvinyl alcohol aerogel: Dry 3% Span 85-modified nano-calcium carbonate was ultrasonically treated for 10 minutes to uniformly disperse it in a hydrochloric acid solution. 0.1 g of initiator AIBN and 0.5 g of binder triethanolamine were added, and the mixture was mixed with the 3 mol / L hydrochloric acid-modified activated carbon / polyvinyl alcohol hydrogel to obtain a Span 85-fly limestone / 3 mol / L hydrochloric acid-modified activated carbon / polyvinyl alcohol hydrogel. The composite hydrogel was freeze-dried at -10°C under a vacuum of 5 Pa for 24 hours to remove excess water and air, resulting in a 3% Span 85-nano-calcium carbonate / 3 mol / L hydrochloric acid-modified activated carbon / polyvinyl alcohol aerogel.

[0041] Example 2

[0042] A method for preparing a double-modified polyvinyl alcohol aerogel, the specific process is as follows:

[0043] Step 1, pretreatment of fly ash stone: fly ash stone is used as raw material, hydrochloric acid is selected as the pretreatment liquid, the pH value of the pretreatment liquid is 3.5, and the fly ash stone sample is first mixed with the pretreatment solution by double decomposition method and filtered. Then, oleic acid and ethanol solution are added to the filtrate and saturated sodium carbonate solution is added dropwise to obtain 40nm nano-calcium carbonate precipitate, filtered, and dried at a temperature of 40°C for 2.5h to obtain dry 40nm nano-calcium carbonate powder.

[0044] Step 2: Mixing the dried nano-calcium carbonate powder with 5% by mass of the ester compound Span 85: The nano-calcium carbonate powder and anhydrous ethanol were mixed in a 1:2 mass ratio and heated in a water bath to 50°C. Ultrasonication was then performed for 10 minutes to uniformly disperse the mixture. 5% Span 85 was then added and heated with stirring for 40 minutes. After the reaction was complete, the mixture was cooled to room temperature and filtered, washed with anhydrous ethanol, and dried at 90°C to obtain 5% Span 85-modified nano-calcium carbonate.

[0045] Step 3, 3.5 mol / L hydrochloric acid modified activated carbon / polyvinyl alcohol hydrogel experiment: first, add polyvinyl alcohol powder to deionized water and dissolve it at 80°C to obtain a polyvinyl alcohol solution. Secondly, add 3 g of activated carbon to 10 mL of 3.5 mol / L hydrochloric acid, stir in a 40°C water bath for 7 hours, wash with deionized water until neutral, filter, and dry in a 90°C drying oven for 24 hours to obtain modified activated carbon. Finally, dissolve the dried modified activated carbon and polymerize it with the polyvinyl alcohol solution at a mass fraction of 5% for 6 hours. During the solution polymerization process, NaOH was added dropwise to adjust the pH value to 4 to obtain 3.5 mol / L hydrochloric acid modified activated carbon / polyvinyl alcohol hydrogel.

[0046] Step 4, preparation of 5% Span 85-nano-calcium carbonate / 3.5 mol / L hydrochloric acid-modified activated carbon / polyvinyl alcohol aerogel: dry 5% Span 85-modified nano-calcium carbonate was ultrasonically treated for 10 minutes and uniformly dispersed in a hydrochloric acid solution. 0.1 g of initiator AIBN and 0.5 g of binder triethanolamine were added and mixed with the 3.5 mol / L hydrochloric acid-modified activated carbon / polyvinyl alcohol hydrogel to obtain 5% Span 85-fly limestone / 3.5 mol / L hydrochloric acid-modified activated carbon / polyvinyl alcohol hydrogel. The composite hydrogel was freeze-dried at -20°C and vacuum at 5 Pa for 24 hours to remove excess water and air, thereby obtaining 5% Span 85-nano-calcium carbonate / 3.5 mol / L hydrochloric acid-modified activated carbon / polyvinyl alcohol aerogel.

[0047] Example 3

[0048] A method for preparing a double-modified polyvinyl alcohol aerogel, the specific process is as follows:

[0049] Step 1, pretreatment of fly ash stone: fly ash stone is used as raw material, hydrochloric acid is selected as the pretreatment solution, the pH value of the pretreatment solution is 4.5, and the fly ash stone sample is first mixed with the pretreatment solution by double decomposition method and filtered. Then, oleic acid and ethanol solution are added to the filtrate and saturated sodium carbonate solution is added dropwise to obtain 50nm nano-calcium carbonate precipitate, filtered, and dried at a temperature of 45°C for 2.5h to obtain dry 50nm nano-calcium carbonate powder.

[0050] Step 2: Mixing the dried nano-calcium carbonate powder with 3% by mass of the ester compound Span 80: The nano-calcium carbonate powder and anhydrous ethanol were mixed in a mass ratio of 1:5 and heated in a water bath. After heating to 55°C, the mixture was ultrasonically dispersed for 15 minutes. 3% Span 80 was then added and heated and stirred for 60 minutes. After the reaction was complete, the mixture was cooled to room temperature and filtered. The mixture was washed with anhydrous ethanol and dried at 100°C to obtain 3% Span 80-modified nano-calcium carbonate.

[0051] Step 3, 4 mol / L hydrochloric acid modified activated carbon / polyvinyl alcohol hydrogel experiment: first, add polyvinyl alcohol powder to deionized water and dissolve it at 85°C to obtain a polyvinyl alcohol solution. Secondly, add 4 g of activated carbon to 20 mL of 4 mol / L hydrochloric acid, stir in a 45°C water bath for 6 hours, wash with deionized water until neutral, filter, and dry in a 100°C drying oven for 20 hours to obtain modified activated carbon. Finally, dissolve the dried modified activated carbon and polymerize it with the polyvinyl alcohol solution at a mass fraction of 10% for 5 hours. During the solution polymerization process, NaOH is added dropwise to adjust the pH value to 5 to obtain 4 mol / L hydrochloric acid modified activated carbon / polyvinyl alcohol hydrogel.

[0052] Step 4, preparation of 3% Span 80-nano-calcium carbonate / 4 mol / L hydrochloric acid-modified activated carbon / polyvinyl alcohol aerogel: dry 3% Span 80-modified nano-calcium carbonate was ultrasonically treated for 15 minutes and uniformly dispersed in a hydrochloric acid solution. 0.3 g of initiator AIBN and 0.7 g of binder triethanolamine were added and mixed with the 4 mol / L hydrochloric acid-modified activated carbon / polyvinyl alcohol hydrogel to obtain 3% Span 80-fly limestone / 4 mol / L hydrochloric acid-modified activated carbon / polyvinyl alcohol hydrogel. The composite hydrogel was freeze-dried at -30°C and vacuum at 10 Pa for 22 hours to remove excess water and air, thereby obtaining 3% Span 80-nano-calcium carbonate / 4 mol / L hydrochloric acid-modified activated carbon / polyvinyl alcohol aerogel.

[0053] Example 4

[0054] A method for preparing a double-modified polyvinyl alcohol aerogel, the specific process is as follows:

[0055] Step 1, pretreatment of fly ash stone: fly ash stone is used as raw material, hydrochloric acid is selected as the pretreatment solution, the pH value of the pretreatment solution is 4.5, and the fly ash stone sample is first mixed with the pretreatment solution by double decomposition method and filtered. Then, oleic acid and ethanol solution are added to the filtrate and saturated sodium carbonate solution is added dropwise to obtain 60nm nano-calcium carbonate precipitate, filtered, and dried at a temperature within the range of 45°C for 2h to obtain dry 60nm nano-calcium carbonate powder.

[0056] Step 2: Mixing the dried nano-calcium carbonate powder with an ester compound Span 80 at a mass fraction of 5%: The nano-calcium carbonate powder and anhydrous ethanol are mixed at a mass ratio of 1:5 and heated in a water bath. After heating to 55° C., ultrasonication is performed for 15 minutes to uniformly disperse the mixture. Subsequently, 5% Span 80 is added and heated and stirred for 60 minutes. After the reaction is completed, the mixture is cooled to room temperature and filtered, washed with anhydrous ethanol, and dried at 100° C. to obtain 5% Span 80-modified nano-calcium carbonate.

[0057] Step 3, 4.5 mol / L hydrochloric acid modified activated carbon / polyvinyl alcohol hydrogel experiment: first, add polyvinyl alcohol powder to deionized water and dissolve it at 85°C to obtain a polyvinyl alcohol solution. Secondly, add 5 g of activated carbon to 20 mL of hydrochloric acid with a concentration of 4.5 mol / L. After stirring in a 45°C water bath for 6 hours, wash with deionized water until neutral, filter, and dry in a 100°C drying oven for 18 hours to obtain modified activated carbon. Finally, dissolve the dried modified activated carbon and polymerize it with the polyvinyl alcohol solution in a mass fraction range of 10% for 5 hours. During the solution polymerization process, NaOH was added dropwise to adjust the pH value to 5 to obtain 4.5 mol / L hydrochloric acid modified activated carbon / polyvinyl alcohol hydrogel.

[0058] Step 4, preparation of 5% Span 80-nano-calcium carbonate / 4.5 mol / L hydrochloric acid-modified activated carbon / polyvinyl alcohol aerogel: dry 5% Span 80-modified nano-calcium carbonate was ultrasonically treated for 15 minutes and uniformly dispersed in a hydrochloric acid solution. 0.3 g of initiator AIBN and 0.7 g of binder triethanolamine were added and mixed with the 4.5 mol / L hydrochloric acid-modified activated carbon / polyvinyl alcohol hydrogel to obtain a 5% Span 80-fly limestone / 4.5 mol / L hydrochloric acid-modified activated carbon / polyvinyl alcohol hydrogel. The composite hydrogel was freeze-dried at -40°C and vacuum at 15 Pa for 20 hours to remove excess water and air, thereby obtaining a 5% Span 80-nano-calcium carbonate / 4.5 mol / L hydrochloric acid-modified activated carbon / polyvinyl alcohol aerogel.

[0059] Example 5

[0060] A method for preparing a double-modified polyvinyl alcohol aerogel, the specific process is as follows:

[0061] Step 1, pretreatment of fly ash stone: fly ash stone is used as raw material, hydrochloric acid is selected as the pretreatment solution, the pH value of the pretreatment solution is 5.5, and the fly ash stone sample is first mixed with the pretreatment solution by double decomposition method and filtered. Then, oleic acid and ethanol solution are added to the filtrate and saturated sodium carbonate solution is added dropwise to obtain 70nm nano-calcium carbonate precipitate, filtered, and dried at a temperature within the range of 50°C for 2h to obtain dry 70nm nano-calcium carbonate powder.

[0062] Step 2: Mixing the dried nano-calcium carbonate powder with 3% by mass of an ester compound, Span 65: The nano-calcium carbonate powder and anhydrous ethanol are mixed in a mass ratio of 1:6 and heated in a water bath. After heating to 60° C., the mixture is ultrasonicated for 20 minutes to uniformly disperse the mixture. Subsequently, 3% Span 65 is added and heated and stirred for 80 minutes. After the reaction is completed, the mixture is cooled to room temperature and filtered, washed with anhydrous ethanol, and dried at 110° C. to obtain 3% Span 65-modified nano-calcium carbonate.

[0063] Step 3, 5 mol / L hydrochloric acid modified activated carbon / polyvinyl alcohol hydrogel experiment: first, add polyvinyl alcohol powder to deionized water and dissolve it at 90°C to obtain a polyvinyl alcohol solution. Secondly, add 6 g of activated carbon to 30 mL of 5 mol / L hydrochloric acid, stir in a 50°C water bath for 5 hours, wash with deionized water until neutral, filter, and dry in a 110°C drying oven for 16 hours to obtain modified activated carbon. Finally, dissolve the dried modified activated carbon and polymerize it with the polyvinyl alcohol solution at a mass fraction of 15% for 4 hours. During the solution polymerization process, NaOH was added dropwise to adjust the pH value to 7 to obtain 5 mol / L hydrochloric acid modified activated carbon / polyvinyl alcohol hydrogel.

[0064] Step 4, preparation of 3% Span 65-nano-calcium carbonate / 5 mol / L hydrochloric acid-modified activated carbon / polyvinyl alcohol aerogel: dry 3% Span 65-modified nano-calcium carbonate was ultrasonically treated for 20 minutes and uniformly dispersed in a hydrochloric acid solution. 0.7 g of initiator AIBN and 1 g of binder triethanolamine were added and mixed with the 5 mol / L hydrochloric acid-modified activated carbon / polyvinyl alcohol hydrogel to obtain 3% Span 65-fly limestone / 5 mol / L hydrochloric acid-modified activated carbon / polyvinyl alcohol hydrogel. The composite hydrogel was freeze-dried at -50°C and vacuum at 20 Pa for 18 hours to remove excess water and air, thereby obtaining 3% Span 65-nano-calcium carbonate / 5 mol / L hydrochloric acid-modified activated carbon / polyvinyl alcohol aerogel.

[0065] Example 6

[0066] A method for preparing a double-modified polyvinyl alcohol aerogel, the specific process is as follows:

[0067] Step 1, pretreatment of fly ash stone: fly ash stone is used as raw material, hydrochloric acid is selected as the pretreatment solution, the pH value of the pretreatment solution is 5.5, and the fly ash stone sample is first mixed with the pretreatment solution by double decomposition method and filtered. Then, oleic acid and ethanol solution are added to the filtrate and saturated sodium carbonate solution is added dropwise to obtain 80nm nano-calcium carbonate precipitate, filtered, and dried at a temperature within the range of 50°C for 2h to obtain dry 80nm nano-calcium carbonate powder.

[0068] Step 2: Mixing the dried nano-calcium carbonate powder with an ester compound Span 65 at a mass fraction of 5%: The nano-calcium carbonate powder and anhydrous ethanol are mixed at a mass ratio of 1:6 and heated in a water bath. After heating to 60° C., ultrasonication is performed for 20 minutes to uniformly disperse the mixture. Subsequently, 5% Span 65 is added and heated and stirred for 80 minutes. After the reaction is completed, the mixture is cooled to room temperature and filtered, washed with anhydrous ethanol, and dried at 110° C. to obtain 5% Span 65-modified nano-calcium carbonate.

[0069] Step 3, 5.5 mol / L hydrochloric acid modified activated carbon / polyvinyl alcohol hydrogel experiment: first, add polyvinyl alcohol powder to deionized water and dissolve it at 95°C to obtain a polyvinyl alcohol solution. Secondly, add 7 g of activated carbon to 30 mL of 5.5 mol / L hydrochloric acid, stir in a 50°C water bath for 5 hours, wash with deionized water until neutral, filter, and dry in a 110°C drying oven for 14 hours to obtain modified activated carbon. Finally, dissolve the dried modified activated carbon and polymerize it with the polyvinyl alcohol solution at a mass fraction of 15% for 4 hours. During the solution polymerization process, NaOH was added dropwise to adjust the pH value to 7 to obtain 5.5 mol / L hydrochloric acid modified activated carbon / polyvinyl alcohol hydrogel.

[0070] Step 4, preparation of 5% Span 65-nano-calcium carbonate / 5.5 mol / L hydrochloric acid-modified activated carbon / polyvinyl alcohol aerogel: dry 5% Span 65-modified nano-calcium carbonate was ultrasonicated for 20 minutes and uniformly dispersed in a hydrochloric acid solution. 0.7 g of initiator AIBN and 1 g of binder triethanolamine were added and mixed with the 5.5 mol / L hydrochloric acid-modified activated carbon / polyvinyl alcohol hydrogel to obtain 5% Span 65-fly limestone / 5.5 mol / L hydrochloric acid-modified activated carbon / polyvinyl alcohol hydrogel. The composite hydrogel was freeze-dried at -60°C and vacuum at 25 Pa for 16 hours to remove excess water and air, thereby obtaining 5% Span 65-nano-calcium carbonate / 5.5 mol / L hydrochloric acid-modified activated carbon / polyvinyl alcohol aerogel.

[0071] Example 7

[0072] A method for preparing a double-modified polyvinyl alcohol aerogel, the specific process is as follows:

[0073] Step 1, pretreatment of fly ash stone: fly ash stone is used as raw material, hydrochloric acid is selected as the pretreatment solution, the pH value of the pretreatment solution is 6.5, and the fly ash stone sample is first mixed with the pretreatment solution by double decomposition method and filtered. Then, oleic acid and ethanol solution are added to the filtrate and saturated sodium carbonate solution is added dropwise to obtain 90nm nano-calcium carbonate precipitate, filtered, and dried at a temperature of 55°C for 1.5h to obtain dry 90nm nano-calcium carbonate powder.

[0074] Step 2: Mixing the dried nano-calcium carbonate powder with 3% by mass of the ester compound Span 60: The nano-calcium carbonate powder and anhydrous ethanol were mixed in a mass ratio of 1:8 and heated in a water bath. After heating to 70°C, the mixture was ultrasonically dispersed for 30 minutes. 3% Span 60 was then added and heated and stirred for 90 minutes. After the reaction was complete, the mixture was cooled to room temperature and filtered. The mixture was washed with anhydrous ethanol and dried at 120°C to obtain 3% Span 60-modified nano-calcium carbonate.

[0075] Step 3, 6 mol / L hydrochloric acid modified activated carbon / polyvinyl alcohol hydrogel experiment: First, polyvinyl alcohol powder was added to deionized water and dissolved at 100°C to obtain a polyvinyl alcohol solution. Next, 8 g of activated carbon was added to 40 mL of 6 mol / L hydrochloric acid. After stirring in a 60°C water bath for 4 hours, it was washed with deionized water until neutral, filtered, and dried in a 120°C drying oven for 12 hours to obtain modified activated carbon. Finally, the dried modified activated carbon was dissolved and polymerized with the polyvinyl alcohol solution at a mass fraction of 20% for 3 hours. During the solution polymerization process, NaOH was added dropwise to adjust the pH to 8 to obtain a 6 mol / L hydrochloric acid modified activated carbon / polyvinyl alcohol hydrogel.

[0076] Step 4, preparation of 3% Span 60-nano calcium carbonate / 6 mol / L hydrochloric acid modified activated carbon / polyvinyl alcohol aerogel: dry 3% Span 60 modified nano calcium carbonate was ultrasonically treated for 30 minutes and uniformly dispersed in a hydrochloric acid solution. 1 g of initiator AIBN and 1.5 g of binder triethanolamine were added and mixed with the 6 mol / L hydrochloric acid modified activated carbon / polyvinyl alcohol hydrogel to obtain 3% Span 60-fly limestone / 6 mol / L hydrochloric acid modified activated carbon / polyvinyl alcohol hydrogel. The composite hydrogel was freeze-dried at -70°C and vacuum at 30 Pa for 14 hours to remove excess water and air, thereby obtaining 3% Span 60-nano calcium carbonate / 6 mol / L hydrochloric acid modified activated carbon / polyvinyl alcohol aerogel.

[0077] Example 8

[0078] A method for preparing a double-modified polyvinyl alcohol aerogel, the specific process is as follows:

[0079] Step 1, pretreatment of fly ash stone: fly ash stone is used as raw material, hydrochloric acid is selected as the pretreatment solution, the pH value of the pretreatment solution is 6.5, and the fly ash stone sample is first mixed with the pretreatment solution by double decomposition method and filtered. Then, oleic acid and ethanol solution are added to the filtrate and saturated sodium carbonate solution is added dropwise to obtain 100nm nano-calcium carbonate precipitate, filtered, and dried at a temperature of 60°C for 1.5h to obtain dry 100nm nano-calcium carbonate powder.

[0080] Step 2: Mixing the dried nano-calcium carbonate powder with 5% by mass of an ester compound, Span 60: The nano-calcium carbonate powder and anhydrous ethanol are mixed in a mass ratio of 1:8 and heated in a water bath. After heating to 70° C., ultrasonication is performed for 30 minutes to uniformly disperse the mixture. Subsequently, 5% Span 60 is added and the mixture is heated and stirred for 90 minutes. After the reaction is completed, the mixture is cooled to room temperature and filtered, washed with anhydrous ethanol, and dried at 120° C. to obtain 5% Span 60-modified nano-calcium carbonate.

[0081] Step 3, 7mol / L hydrochloric acid modified activated carbon / polyvinyl alcohol hydrogel experiment: first, add polyvinyl alcohol powder to deionized water and dissolve it at 100°C to obtain a polyvinyl alcohol solution. Secondly, add 8g of activated carbon to 50mL of 7mol / L hydrochloric acid, stir in a 60°C water bath for 4h, wash with deionized water until neutral, filter, and dry in a 120°C drying oven for 12h to obtain modified activated carbon. Finally, dissolve the dried modified activated carbon and polymerize it with the polyvinyl alcohol solution at a mass fraction of 20% for 3h. During the solution polymerization process, NaOH was added dropwise to adjust the pH value to 8 to obtain 7mol / L hydrochloric acid modified activated carbon / polyvinyl alcohol composite hydrogel.

[0082] Step 4, preparation of 5% Span 60-nano calcium carbonate / 6.5 mol / L hydrochloric acid modified activated carbon / polyvinyl alcohol aerogel: dry 5% Span 60 modified nano calcium carbonate was ultrasonically treated for 30 minutes and uniformly dispersed in a hydrochloric acid solution. 1 g of initiator AIBN and 1.5 g of binder triethanolamine were added and mixed with 7 mol / L hydrochloric acid modified activated carbon / polyvinyl alcohol hydrogel to obtain 5% Span 60-fly limestone / 7 mol / L hydrochloric acid modified activated carbon / polyvinyl alcohol hydrogel. The composite hydrogel was freeze-dried at -80°C and vacuum at 30 Pa for 12 hours to remove excess water and air, thereby obtaining 5% Span 60-nano calcium carbonate / 7 mol / L hydrochloric acid modified activated carbon / polyvinyl alcohol aerogel.

[0083] The oil absorption value and cycle adsorption times of the double-modified polyvinyl alcohol aerogel in the embodiment are compared with the existing oil-absorbing polyvinyl alcohol aerogel test results as shown in the following table:

[0084]

[0085]

[0086] As can be seen from the table above, compared with pure silica aerogel and graphene oxide aerogel, the double-modified polyvinyl alcohol aerogel prepared by the present invention can increase the porosity and specific surface area of activated carbon by etching with hydrochloric acid, and with the help of free Ca in nano-calcium carbonate contained in fly ash stone, the surface area of activated carbon can be increased. 2+ The interaction with the ester groups in ester compounds can further enhance the adsorption of nano-calcium carbonate. Furthermore, the two are firmly bonded to the high-surface-area polyvinyl alcohol aerogel through polymerization, blending, and freeze-drying under the action of an initiator and a binder. This results in the aerogel prepared by the present invention having significantly improved oil absorption and recyclability compared to other novel porous oil-absorbing materials. In summary, the preparation method of the double-modified polyvinyl alcohol aerogel prepared by the present invention has extremely strong oil absorption and high recyclability, and is expected to have wide application in the field of petroleum pollution control.

[0087] Although specific embodiments of the present invention have been described above, those skilled in the art will appreciate that these are merely illustrative and that the scope of the present invention is defined by the appended claims. Those skilled in the art may make various changes or modifications to these embodiments without departing from the principles and essence of the present invention, and such changes and modifications are intended to fall within the scope of the present invention.

Claims

1. A method for preparing a double-modified polyvinyl alcohol aerogel, characterized in that: The following steps are involved: Step 1, pretreatment of fly ash stone: using fly ash stone as raw material, selecting hydrochloric acid as pretreatment solution, the pH value of the pretreatment solution is 3.5-6.5, using double decomposition method to first mix the fly ash stone sample with the pretreatment solution and filter, adding oleic acid and ethanol solution to the filtrate and adding saturated sodium carbonate solution dropwise to obtain nano calcium carbonate precipitate, filtering, and drying to obtain nano calcium carbonate powder; Step 2: mixing the nano-calcium carbonate powder obtained in step 1 with anhydrous ethanol, heating the mixture in a water bath, and uniformly dispersing the mixture by ultrasonication; then adding one of the ester compounds Span85, Span80, Span65, and Span60, heating and stirring the mixture; cooling the mixture to room temperature after the reaction is completed, filtering the mixture, washing the mixture with anhydrous ethanol, and drying the mixture to obtain modified nano-calcium carbonate; Step 3: First, polyvinyl alcohol powder is added to deionized water and dissolved at 80°C to 100°C to obtain a polyvinyl alcohol solution. Then, activated carbon is added to 10 to 50 mL of hydrochloric acid, stirred in a water bath at 40 to 60°C for 4 to 7 hours, washed with deionized water until neutral, filtered, and dried in a drying oven at 90°C to 120°C for 12 to 24 hours to obtain modified activated carbon. Finally, the dried modified activated carbon is dissolved and polymerized with the polyvinyl alcohol solution. During the solution polymerization process, NaOH is added dropwise to adjust the pH value to 5 to 8 to obtain a hydrochloric acid-modified activated carbon / polyvinyl alcohol hydrogel with extremely strong hydrophobicity. Step 4, freeze-drying method to prepare ester compound modified fly ash stone / hydrochloric acid modified activated carbon / polyvinyl alcohol aerogel: the modified nano calcium carbonate obtained in step 2 is ultrasonically treated for 10 to 30 minutes, uniformly dispersed in a hydrochloric acid solution, initiator AIBN and adhesive triethanolamine are added, and mixed with the hydrochloric acid modified activated carbon / polyvinyl alcohol hydrogel obtained in step 3 to obtain ester compound-nano calcium carbonate / hydrochloric acid modified activated carbon / polyvinyl alcohol hydrogel, and the ester compound-nano calcium carbonate / hydrochloric acid modified activated carbon / polyvinyl alcohol hydrogel is dried at a temperature of -10°C to -80°C and a vacuum of 5 to 30 Pa for 12 to 24 hours to remove excess moisture and air to obtain a dry ester compound-nano calcium carbonate / hydrochloric acid modified activated carbon / polyvinyl alcohol aerogel, that is, a double-modified polyvinyl alcohol aerogel.

2. The method for preparing a double-modified polyvinyl alcohol aerogel according to claim 1, wherein: The particle size of the nano calcium carbonate powder obtained in step 1 ranges from 30 to 100 nm.

3. The method for preparing a double-modified polyvinyl alcohol aerogel according to claim 1, characterized in that: The drying temperature in step 1 is 40-60° C., and the drying time is 1.5-2.5 hours.

4. The method for preparing a double-modified polyvinyl alcohol aerogel according to claim 1, wherein: The mass fraction of the ester compounds Span85, Span80, Span65, and Span60 selected in step 2 is 3% or 5%.

5. The method for preparing a double-modified polyvinyl alcohol aerogel according to claim 1, characterized in that: The mass ratio of the nano-calcium carbonate powder to anhydrous ethanol in step 2 is 1:2 to 1:8, the water bath heating temperature is 50°C to 70°C, the ultrasonic dispersion time is 10 to 30 minutes, the heating and stirring time is 40 to 90 minutes, and the drying temperature is 90 to 120°C.

6. The method for preparing a double-modified polyvinyl alcohol aerogel according to claim 1, characterized in that: The hydrochloric acid concentration in step 3 is in the range of 3% to 7%, and the activated carbon mass is 2 to 8 g.

7. The method for preparing a double-modified polyvinyl alcohol aerogel according to claim 1, characterized in that: After the modified activated carbon described in step 3 is dissolved, it is polymerized with the polyvinyl alcohol solution in a mass fraction range of 5%, 10%, 15%, and 20% for 3 to 6 hours.

8. The method for preparing a double-modified polyvinyl alcohol aerogel according to claim 1, characterized in that: In step 4, the mass of the initiator AIBN is 0.1-1 g, and the mass of the adhesive triethanolamine is 0.5-1.5 g.

9. Use of the double-modified polyvinyl alcohol aerogel prepared by the method for preparing the double-modified polyvinyl alcohol aerogel according to any one of claims 1 to 8 in petroleum pollution control.

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